German officials struggled on Monday to pinpoint the source of a deadly E. coli outbreak after initial tests on bean sprouts grown at a farm near Hamburg showed no traces of the bacteria.
The farm in Bienenbuettel, Lower Saxony was named as the source on Sunday but 23 samples have shown up negative.
Authorities are still waiting for results from 17 more tests.
German Agricultural Minister Ilse Aigner said the government would continue to be vigilant until all the results had been compiled.
The rare strain of E. coli has killed 21 people in Germany and one person in Sweden.
It has also left nearly 2,300 people ill across Europe and prompted Russia to ban all fresh vegetable imports from the European Union.
Germany had initially incorrectly identified Spanish cucumbers as the source of the problem.
They have now been given the all-clear but farmers in Spain have been hit by slumping sales as shoppers shun their produce.
Their losses are estimated to be close to 200 million euros per week and they are now demanding compensation.